Over 1,500,000 percutaneous coronary procedures are performed worldwide each year. Current diagnostic methods are based on detection of flow limiting atherosclerotic lesions by lumenal morphometry (x-ray angiography, intravascular ultrasound) or secondary myocardial ischemia (ECG changes, nuclear scintigraphy perfusion defects). The majority of myocardial infarctions result from rupture of non-flow limiting lesions. Magnetic resonance imaging produces excellent soft tissue contrast based on biochemical structure and does not use ionizing radiation and can produce spatial resolution superior to current x-ray systems. It can differentiate between plaque components including lipids, calcium, connective tissue and thrombus. To achieve the level of signal-to-noise required for high resolution imaging, intravascular receiver coils have been proposed. Current designs require conducting wires with the potential for heating and limited data bandwidth which precludes incorporation of other physiological sensors into the catheter. We will develop a fully fiber-optic magnetic resonance imaging catheter with performance characteristics equal, or superior to existing wire-based devices. In Phase I we will design, construct and test large scale individual opto-electronic sub-assemblies. In Phase II, sub-assemblies will be miniaturized into a 3F operational catheter. Aim 1: Design and test fiber-optic based system for converting multiple analog electrical signals produced in radio-frequence coil(s) and physiological sensing units to optical signal, transmit signal along optical fiber and convert back to electrical signal with high signal-to-noise and without distortion. Aim 2: Design and lest an optical power supply (light source) producing electrical current for the circuits described in aims 1 and 2 utilizing a laser light source external to the catheter imaging/sensing system. Aim 3: lntegrate a fiber-optic based temperature sensor into the prototype utilizing the optical signal transmission system of aim 1, and the power source developed in aim 2.